The jumping of batteries via the use of jumper cables has been known in the past in which one battery is charged via another battery through the utilization of jumper cables which carry large currents. One of the problems with the utilization of such cables is the possibility of polarity reversal which causes a large amount of sparking that is both frightening and can, in fact, ignite some of the battery gases or other flammable materials within the engine compartment should the polarity be reversed when the cables are connected. While those skilled in the utilization battery cables, including auto mechanics and the like, have very little difficulty in ascertaining the polarity of batteries and whether or not a battery is capable of being charged, the utilization of battery cables by those not skilled in battery cable interconnection has resulted in either the non-use of battery jumper cables or the incorrect use of the cables which, at the very least, does not result in the proper battery being charged from a presumably "good" battery.
This situation is made more complicated and mistakes can be made because when batteries are in most need of charging, it is usually in cold weather or in the pouring rain, in which mistakes can be made due to the inclement conditions under which most battery jumping occurs. Also, dirt on, or corrosion of wires and terminals may be so great that the polarity of the battery to be charged cannot be easily ascertained. If the batteries are misconnected, the battery may overheat and even explode which can shower people with sulfuric acid. Moreover, highly explosive hydrogen gas is released from the car battery and can be ignited, in some instances, by a single spark.
There is, therefore, a need a for the sensing of the polarity of both batteries, ensuring that at least one of the batteries has sufficient charge to charge the bad battery, and also ensuring that the bad battery is not discharged so low that it is a risk to charge. There is therefore need for a system which ascertains when all of the conditions for proper charge have been met, and then to properly connect the batteries together. Thus, there is a necessity for an automatic jumper cable system which ascertains all of the above conditions and only connects the batteries together under an appropriate set of conditions. Moreover, the system must protect against inadvertently shorting the jaws of the cable clamps together which causes a rain of sparks that automatically discharges either one or both of the batteries. This is a frequenct situation since the battery jaws common on most jumper cables have exposed electrically conductive elements.